Motorcycle Repair: Yamaha 1983 Virago 920, bike bandit, spark plug wire

Question
Mark, thanks for your response to my other question works well. Now that the carb works great I have been dealing with another prob. It seems every now and then my bike will backfire while running down the road along with my rear cylinder plug fouling. When I take off the spark plug wire and touch it to the motor it emits a spark, and on the front no such thing. Here's my question plug wire replacement or coil because either one is extremely expensive according to some of the websites I have gone to and I am about up to here with it. The coil for the rear cylinder also feels a little warmer than the other as well. Any info or websites for cheap parts and/or recommendations would be a great help. Like I had told you before I am trying to do as much as I can by myself so I understand the bike and can fix/repair it if I need on the road.

Thanks Again

J

Answer
Hi J,

The arcing is a problem with the rear secondary lead (plug wire). The cap or wire is likely defective. Electrical current should not leak to ground as you've described. Oil and road grime (dirty engine) may conduct current to ground. Try cleaning the plug wire and cap. The coil may be in good condition. They rarely go bad.

The rear coil may be hotter due to lack of cooling. The rear cylinder's carburetor is jetted richer than the front to help keep the hotter running rear cylinder cooler. Rear cylinders don't get the forced convection (air cooling) as front cylinders. Warmer temperature coil may be normal.

Try Bike Bandit "www.bikebandit.com" for parts price comparison and viewing microfiche on line.

Otherwise, check Ebay for replacement parts for your Virago.

Respectfully,
Mark Shively




Dielectric Grease Therapy



Here's a fairly quick and inexpensive way of preventing electrical problems and other miscellaneous diagnostic codes on your motorcycle.

Water is a great electricity conductor. Sometimes, water can find its way into a connector producing a temporary short circuit which will then give an error code to your computers. Dielectric grease prevents water shorting at connectors. Also prevents corrosion formation on connectors.

A loose connector doesn't make a good conductor and may produce heat which can melt plugs and connectors. This is the main cause of regulator/rectifier failure.

Buy a tube of silicone dielectric grease and go through the entire wiring on your motorcycle. Work dielectric grease into each connector. All wire connectors should be serviced for best protection. Removing the tank and bodywork may be necessary in some cases, but its well worth it. Dielectric grease will get rid of the problems, or at least help prevent them.

Afterwards, you shouldn't get false error diagnostic codes just because you simply washed your pride and joy.
You may discover loose connectors that could have been troublesome if left unattended.